Vitamin D is also called the Sunshine Vitamin because it is synthesized in the skin from cholesterol on exposure to the sun.

Vitamin D is a unique vitamin since it can be produced in sufficient quantity in the body.

Other vitamins are not synthesized in sufficient amounts in humans. Still vitamin D fulfills the second requirement of vitamins: it is an essential nutrient needed in very small amounts.

Vitamin D is a group of five fat-soluble secosteroids. The two most common forms of the vitamin are Ergocalciferol or vitamin D2 or Cholecalciferol or vitamin D3. Both forms of the vitamin can be ingested.

Vitamin D is converted to the prohormone, calcidiol in the liver which is then converted to calcitriol in the kidneys and in the macrophage cells of the immune system.

Calcitriol, which is the bioactive form of vitamin D, is then released into the blood.

Calcitriol is a hormone that regulates calcium and phosphate levels in the blood and so promotes bone health. It is also important to the inflammatory process and neuromuscular function.

Besides its production in the skin on exposure to sunlight, vitamin D can also be obtained from food sources.

Dietary sources of vitamin D

Vitamin D2 can be found in alfalfa and mushrooms.

Vitamin D3 can be found in fatty fish such as catfish, salmon, mackerel, tuna and sardines; eggs, beef liver and fish liver.

In the US, the recommended daily vitamin D intake is 15 micrograms per day or 600 IU/day. Upper intake limit for adults is however 4,000 IU.

The major symptom of vitamin D deficiency is a disease called rickets. It causes the softening of the bones. A related disease of the bone called osteomalacia is also caused by vitamin D deficiency.

Vitamin D toxicity is also possible. It can be caused by ingesting very high doses (about 50,000 IU) of the vitamin for several months.

Vitamin D toxicity causes hypercalcemia. Therefore, its symptoms are the same as the symptoms for hypercalcemia. These include nausea, vomiting, excessive urination and thirst, weakness, insomnia and pruritus.

In the body, the active form of calcitriol binds to carrier proteins which then distribute it to different organs.

When calcitriol is produced by the cells of the immune system, its primary role is to fight off infections. However, calcitriol produced in the kidneys is responsible for regulating calcium and phosphate.

Calcitriol binds to Vitamin D receptors or VDRs. These receptors can be found in major organs include the brain, heart, gonads, prostate and skin. Therefore, vitamin D can regulate the production of male sex hormones (gonads) and directly produce certain effects on the skin

Vitamin D is already used for the treatment of other skin diseases like psoriasis. Many acne sufferers who commenced vitamin D supplementation report improvement in their symptoms.

While it may seem that there is little solid scientific evidence to back the efficacy of vitamin D in acne therapy, the truth is that most studies have not directly investigated the link even though there are strong indications that such link exists.

Vitamin D seems to be a forgotten supplement in acne treatment. This is because one of the best studies on the relationship between the vitamin and acne was done in 1938 and it already established a positive link between the two.

In this study, 5,000 – 40,000 IU per day of vitamin D was given to study participants suffering from severe acne.

This supplementation “cured” 47% of the participants within 3 months while an additional 27% reported improvements in their symptoms.

Since vitamin D is found in animal milk and even added to milk products, some have argued that it might be responsible for the acne breakouts sometimes triggered by milk consumption.

However, scientific evidence has shown that vitamin D has nothing to do with the ability of milk and some dairy products to cause acne. Instead, the increase in the levels of in the hormone, insulin-like growth factor-1, is now believed to be responsible for milk-triggered acne.

There are a number of possible mechanisms by which vitamin D, and especially its analogue, vitamin D3, can help prevent and improve acne symptoms. These mechanisms of action are well understood and can easily be the target of vitamin D supplied in supplements.

A study published in 2006 in Experimental Dermatology by J. Reichrath et al. examined the effect of vitamin D on the cells of the sebaceous glands.

The researchers discovered that vitamin D and its analogues suppress cell proliferation in the sebaceous gland.

This effect is possible because the cells of the sebaceous gland have vitamin D receptors (VDRs). Therefore, when vitamin D binds to these receptors, it can inhibit cell proliferation which can help prevent the enlargement of the gland.

The enlargement of the sebaceous gland is the major change caused by male sex hormones in the development of acne.

When this gland is enlarged, sebum production increases exponentially and excess sebum is pushed to the skin surface where it creates an ideal environment for excessive growth of acne-causing bacteria such as Propionibacterium acnes.

By preventing cell proliferation in the sebaceous gland, vitamin D inhibits the acne-causing effects of androgens such as testosterone.

The ability of vitamin D to suppress the enlargement of the sebaceous gland increases with the dose of the supplement given.

Vitamin D has varying effects on the immune system some of which counteract each other. The pro-inflammatory and anti-inflammatory effects of vitamin D are examples of this peculiar behavior.

Vitamin D3 regulates the release and action of immune cells related to inflammatory response. In some cases, the ability of vitamin D to suppress the inflammatory reaction of the immune system is comparable to the actions of immunosuppressant drugs.

This anti-inflammatory effect is so potent that vitamin D analogues are suggested as candidate drugs for treating surface and systemic inflammatory diseases such as dermatitis and lupus.

Different studies have established that vitamin D is a direct regulator of the immune system’s response to attack from infectious agents including bacteria, viruses and parasites.

The antimicrobial response triggered by vitamin D is attributed to a class of compounds called cationic antimicrobial peptides or AMPs.

One popular example of AMPs is a group of compounds called cathelicidins.

These antimicrobial peptides are currently the best candidates for antibiotic-resistant bacteria in development. This is because they are fast acting antibacterial agents and bacteria find it difficult to develop resistance against them.

Since cathelicidins are produced by leukocytes in epithelial cells, vitamin D can stimulate their production in the skin to attack acne-causing bacteria such as P. acnes and Staphylococcus epidermis.

Only some strains of P. acnes cause acne. Others are found on healthy skin and cause no harm.

However, the colonization of the skin by mutated strains of the bacterium causes increased shedding of dead skin cells, and inflammatory cycles which lead to acne breakout.

Vitamin D can stimulate the production of cathelicidins which are natural antibiotics capable of kill off P. acnes and prevent the series of events that cause acne.

The antioxidant effect of vitamin D includes its ability to protect the skin cells against oxidative stress. To do this, it inhibits the activation of certain protein kinases which are switched on by stress.

This protective effect is the subject of a study in which vitamin D was found effective in protecting epidermal cells from ultraviolet radiation and exposure to chemotherapy. It is believed that the anti-inflammatory effect of this vitamin may also be involved in this protective effect.

Vitamin D is also effective for reducing emotional stress caused by acne breakouts.

Some acne patients suffer from bouts of depression, anxiety and emotional distress concerning the state of their skin. There is a biochemical basis for such negative psychological states.

In most of acne patients who are distressed by their condition, it is found that vitamin D levels are usually low while free radical levels are high. Furthermore, the enzyme, MAO (monoamine oxidase) is also found in low amounts.

Both vitamin D and MAO affect the production and actions of serotonin, a neurotransmitter which contributes to mood.

Therefore, it is possible that increased vitamin D supplementation may reduce emotional stress by mopping up harmful free radicals through its antioxidant effect and regulate the production of serotonin.